1,1,2-Trichloro-1,2,2-trifluoroethane (known in the field by the name F113) has been widely used in the industry for cleaning and degreasing solid surfaces of very diverse nature (metal components, glass, plastic, composites), for which an absence—or at least the lowest possible residual content—of impurities, in particular of organic nature, is required. F113 was particularly suitable for this use on account of its non-corrosive nature with respect to the materials used. This product has been used in particular in the field of manufacturing printed circuits, to remove the residues of the substances used to improve the quality of the solders (known by the term soldering fluxes). This removal operation is known in the field as “defluxing”.
Mention may also be made of the applications of F113 to the degreasing of heavy metal components and to the cleaning of high-quality and high-precision mechanical components such as, for example, gyroscopes and military, aerospace or medical equipment. In its various applications, F113 is usually combined with other organic solvents (for example methanol), in order to improve its cleaning capacity. In this case, it is preferred to use azeotropic or quasi-azeotropic mixtures. For the purposes of the present invention, the term “quasi-azeotropic mixture” means a mixture of generally miscible chemical compounds which, under certain specific conditions of proportions, temperature and pressure, boils at a substantially constant temperature while at the same time retaining substantially the same composition. When it is heated to reflux, such a quasi-azeotropic mixture is in equilibrium with a vapour phase whose composition is substantially the same as that of the liquid phase. Such azeotropic or quasi-azeotropic behaviour is desirable to ensure satisfactory functioning of the machines in which the abovementioned cleaning operations are carried out, and in particular to ensure recycling by distillation of the cleaning fluid.
F113 is also used in fields, in particular in optics, for which it is necessary to have available water-free surfaces, i.e. surfaces on which water is only present at trace levels which are undetectable by the method of measurement (Karl Fisher method). With this aim, F113 is used in operations for cleaning (or dewetting) the said surfaces, in combination with hydrophobic surfactants.
However, the use of compositions based on F113 is now banned since F113 is among the chlorofluorocarbons (CFCs) suspected of attacking or degrading stratospheric ozone.
In these various applications, F113 can be replaced with 1,1-dichloro-1-fluoroethane (known by the name F141b), but the use of this substitute is already regulated since, although weak, its destructive effect on ozone is not non-existent.
Patent application EP 0,512,885 describes a composition comprising from 93 to 99% by weight of 1,1,1,3,3-pentafluorobutane and from 1 to 7% of methanol, which can be used as a substitute for F113. 1,1,1,3,3-Pentafluorobutane, also known in the field by the name F365 mfc, has no destructive effect on ozone.